Flexible screen or sheets such as window screen, plastic films and the like used for various applications including the closing and covering of window openings are well known in the art. Flexible screens or sheets are usually mounted in a frame which is attached to the structure of a window opening. A common material for assembling such frames is an aluminum roll formed section, which is generally an elongated box shaped structure provided with a U-shaped spline groove adjacent an edge of one surface. Four lengths of a roll formed section are commonly assembled into a frame using corner brackets or other fasteners known in the art. A flexible sheet such as window screening is attached to the frame by cutting the sheet to the approximate size of the frame, laying the sheet over that side of the frame which is provided with the spline groove and forcing the sheet into the spline groove with a flexible spline member sized to frictionally engage the sheet with the walls of the spline groove. This is a difficult task which requires a certain amount of skill and experience to install the sheet with even tension and without wrinkling the sheet or warping the frames. In addition, after attaching a flexible sheet to a frame with a conventional spline member, the selvage edges of the sheet must be trimmed to provide a neat appearance and prevent the accidental removal of the sheet from the spline groove by catching the exposed loose edges of the sheet. Trimming the exposed loose edges of the sheet is a tedious and labour intensive task which contributes significantly to the cost of attaching a flexible sheet to a frame.
An alternate method of attaching a flexible sheet to a frame is disclosed in Canadian Patent 1,108,476, which issued on Sept. 8, 1981. This patent describes a fastener for attaching a specially constructed flexible sheet to a frame. The specially constructed flexible sheet is provided along its opposing edges with a permanently attached metallic or plastic extrusion that is gripped by a D-shaped metal fastener. The disadvantage of this method is that the flexible sheet must be precisely dimensioned to the size of the frame opening in order to achieve an acceptable fit, and attaching the required clips is a lengthy and relatively delicate process which is, in itself, time consuming.